In recent years, a solid-state imaging device such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor has used an imaging element that obtains signals of three colors to suppress deterioration in sensitivity. As such an imaging element, for example, PTL 1 discloses a color imaging element including a light reception unit including an organic semiconductor material and a light reception unit including silicon. The organic semiconductor material detects green light and silicon detects each of red light and blue light. The light reception unit that detects green light has a bulk-hetero structure in which a p-type semiconductor and an n-type semiconductor are randomly mixed.
This bulk-hetero structure is a p-n junction surface formed through mixing the p-type semiconductor and the n-type semiconductor, and an exciton charge separation rate in the p-n junction surface significantly influences sensitivity of the imaging element. Accordingly, NTLs 1 to 3 report a method of improving the exciton charge separation rate in the p-n junction surface.